M31N 1926-07c: A Recurrent Nova in M31 with a 2.8 yr Recurrence Time

The M31 recurrent nova M31N 1926-07c has had five recorded eruptions. Well-sampled light curves of the two most recent outbursts, in 2020 January (M31N 2020-01b) and 2022 September (M31N 2022-09a), are presented showing that the photometric evolution of the two events were quite similar, with peak magnitudes of R = 17.2 ± 0.1 and R = 17.1 ± 0.1, and t 2 times of 9.7 ± 0.9 and 8.1 ± 0.5 days for the 2020 and 2022 eruptions, respectively. After considering the dates of the four most recent eruptions (where the cycle count is believed to be known), a mean recurrence interval of 〈P rec〉 = 2.78 ± 0.03 yr is found, establishing that M31N 1926-07c has one of the shortest recurrence times known.